root can not ftp in per the configuration of most ftp servers. the reason you can only see /home/admin is becuase your ftp server is configured to 'chroot' user's to their home directories for securty reasons.

what ftp server are you using, and I can help you configure it otherwise.

For example, I use vsFTPd and the configuration that I use is something like:

With this configuration, all users are chrooted by default, but users listed in "/etc/vsftpd.chroot_list" have unchrooted access to the entire filesystem. (not necessarily recommended if your not using an encrypted connection.)